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The zebra mussel Dreissena polymorpha is one of the most successful, notorious, and detrimental aquatic invasive non‐native species worldwide, having invaded Europe and North America while causing substantial ecological and socio‐economic impacts. Here, we investigated the spatiotemporal trends in this species' invasion success using 178 macroinvertebrate abundance time series, containing 1451 records of D. polymorpha collected across nine European countries between 1972–2019. Using these raw (absolute) abundance data, we examined trends and drivers of occurrences and relative abundances of D. polymorpha within invaded communities. Meta‐regression models revealed non‐significant trends both at the European level and for the majority of the invaded countries, except for France (significant decreasing trend) and Hungary (marginally positive trend). At the European level, the number of D. polymorpha occurrences over time followed a flat‐top bell‐shaped distribution, with a steep increase between 1973–1989 followed by a plateau phase prior to significantly declining post‐1998. Using a series of climatic and hydromorphological site‐specific characteristics of invaded and uninvaded sites from two periods (1998–2002; 2011–2015), we found that native richness, non‐native abundance, distance to the next barrier, and elevation were associated with the occurrence of D. polymorpha. We also found that higher native richness and lower latitude were related to lower relative abundances. Using Cohen's D as a measure of D. polymorpha impact, we found that biodiversity within the invaded sites was initially higher than in uninvaded ones, but then declined, suggesting differences in biodiversity trends across invaded and uninvaded sites. While our results emphasise the high invasion success of D. polymorpha, increasing stressors within the context of global change – particularly ongoing climate change – are likely to enhance invasion rates and the impact of D. polymorpha in the near future, exacerbated by the lack of timely and effective management actions. [ABSTRACT FROM AUTHOR]

Ornamental aquaculture and the related pet industry are known to be important sources of non-native species worldwide. In the temperate zone, thermal waterbodies are attractive places for irresponsible owners to release unwanted freshwater pets including decapod crustaceans. Several non-native ornamental species have been reported in the thermal locality of Miskolctapolca (a suburb of Miskolc, Hungary). So we surveyed this site in March 2019–November 2021 to update local occurrence records and detect potentially newly released species. A well-established population of Neocaridina denticulata and the occurrence of Caridina cf. babaulti had previously been noted. However, for the first time at this site, we found the shrimps Atyopsis moluccensis, Caridina gracilirostris and C. multidentata, as well as the crayfish Procambarus virginalis, P. clarkii, Cherax quadricarinatus, C. boesemani and C. snowden, and several formally undescribed Cherax species originating from New Guinea. Furthermore, in most species, gravid females carrying eggs were also noticed. Three shrimps, A. moluccensis, C. gracilirostris and C. multidentata, were recorded for the first time in European wild. Further monitoring of this locality and better education of the general public regarding the risks associated with the release of non-native species are strongly recommended. [ABSTRACT FROM AUTHOR]

The spread of non-native species results in novel and often unexpected assemblages. Using stable isotopes, we disentangled the trophic relationships between three invasive crayfish species at two sites of a small thermal tributary of the Barát stream, Hungary. We studied Procambarus virginalis and Faxonius limosus living in sympatry in the upper section of this thermal tributary, and then an assemblage in a lower section also containing P. clarkii. The two species in the upper section largely shared trophic niches, although P. virginalis was more carnivorous than F. limosus, which fed more on detritus and aquatic plants. In the lower section, P. clarkii had a distinctive trophic niche, being more carnivorous than the other species and also preying on other crayfish and fish. The trophic niches of the other two species shifted slightly, being narrower and more overlapping in the presence of P. clarkii. It seems that the presence of P. clarkii affects the feeding habits and trophic niches of the other two crayfish. Our results also indicate that the species have somewhat distinctive feeding niches, which suggests that the ecosystem effects of these species are likely to be at least partially additive in the shared localities. [ABSTRACT FROM AUTHOR]

Copyright of Knowledge & Management of Aquatic Ecosystems is the property of EDP Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The pet trade is one of the most important sources of introduction of freshwater non-native decapod crustaceans. Precise and timely identification of potentially hazardous species is necessary for the effective prevention of new introductions. Here, we present a list of species of ornamental freshwater decapod crustaceans pet-traded in Hungary and their risk assessment, including the probability of establishment based on climate matching. The list contains 13 shrimps, eight crayfish, two crabs, and one hermit crab. Three crayfish, Cherax destructor, Procambarus clarkii, P. virginalis, and one crab, Eriocheir sinensis, were classified in the high-risk category. During field sampling, we found three individuals of C. quadricarinatus that were probably released or escaped from aquaria. These are the first records of this species in the wild of Carpathian Basin. We strongly recommend further educating hobbyists about the risks related to the escapes and releases of high-risk taxa, as well as monitoring of the region for their occurrence. [ABSTRACT FROM AUTHOR]

Copyright of Knowledge & Management of Aquatic Ecosystems is the property of EDP Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

[Display omitted] • The capital of Hungary is a hotspot of diversity of introduced ornamental crayfish. • We evaluated whether their release contributes to crayfish plague pathogen spread. • Four species were infected, including Procambarus virginalis, P. clarkii, P. alleni. • We observed unusual associations of Aphanomyces astaci genotypes and host crayfish. • Switch between dominant A. astaci genotypes occurred in one invaded site over time. Ornamental trade has become an important introduction pathway of non-native aquatic species worldwide. Correspondingly, there has been an alarming increase in the number of established crayfish of aquarium origin in Europe over the previous decade. The oomycete Aphanomyces astaci , the pathogen causing crayfish plague responsible for serious declines of European crayfish populations, is dispersed with introduced North American crayfish. The role of ornamental taxa in introducing and spreading different genotypes of this pathogen in open waters remains unclear. We investigated the distribution, prevalence, and diversity of A. astaci in Budapest, Hungary, which became a hotspot of aquarium crayfish introductions. Their establishment in this area was facilitated by locally abundant thermal waters. We screened for A. astaci in six host taxa from 18 sites sampled between 2018 and 2021: five cambarids (Cambarellus patzcuarensis , Faxonius limosus , Procambarus alleni , P. clarkii , P. virginalis) and one native astacid (Pontastacus leptodactylus). The pathogen was confirmed at five sampled sites in four host taxa: P. virginalis, P. clarkii, F. limosus , and for the first time in European open waters also in P. alleni. Genotyping was successful only in individuals from two different brooks where multiple host species coexisted but revealed unexpected patterns. Mitochondrial B-haplogroup of A. astaci , previously usually reported from Pacifastacus leniusculus or infected European species, was detected in P. virginalis at both sites, and in both F. limosus and P. virginalis sampled from a thermally stable tributary of Barát brook in 2018. In contrast, A-haplogroup of A. astaci was detected in coexisting F. limosus , P. virginalis and P. clarkii sampled in the same watercourse just a few hundred meters downstream in 2020. Additional genotyping methods indicated that a previously unknown A. astaci strain was associated with the latter haplogroup. One P. virginalis individual from 2020 was apparently co-infected by strains representing both mitochondrial haplogroups. The results indicated multiple sources of A. astaci in Budapest, likely directly associated with the introduction of ornamental species, interspecific transmission of this pathogen among ornamental hosts, and potential for a quick spatial or temporal turnover of dominant A. astaci strains at a certain locality. This highlights that in regions with high richness of potential A. astaci hosts, host taxon/pathogen genotype combinations become unpredictable, which might prevent reliable genotyping of pathogen sources in local crayfish mass mortalities. [ABSTRACT FROM AUTHOR]

Non-native species introductions have been acknowledged as one of the main drivers of freshwater biodiversity decline worldwide, compromising provided ecosystem services and functioning. Despite growing introduction numbers of non-native species, their impacts in conjunction with anthropogenic stressors remain poorly documented. To fill this gap, we studied temporal changes in α (local scale) and γ (regional scale), as well as β (ratio between γ and α) diversity of non-native freshwater macroinvertebrate species in three European countries (the Netherlands, England and Hungary) using long-term time series data of up to 17 years (2003-2019). We further calculated four ecological and four biological trait metrics to identify changes in trait occurrences over time. We found that α and γ diversities of non-native species were increasing across all countries whereas β diversity remained stable. We did not identify any significant changes in any trait metric over time, while the predictors tested (land use, climatic predictors, site-specific factor) were similar across countries (e.g., site characteristics or climatic predictors on non-native species trends). Additionally, we projected trends of α, β, and γ diversity and trait metrics until 2040, which indicated that non-native species will decline across all countries to lower levels except in England for γ diversity and the Netherlands for α diversity where an increase was observed. Thus, our findings indicate shifts in non-native freshwater macroinvertebrate diversity at both local and regional scales in response to the various growing anthropogenic pressures. Our findings underscore the continuous dynamics of non-native species distribution, with the diversity of individual communities and overall landscapes witnessing changes. However, the differentiation in species composition between communities remains unaltered. This could have profound implications for conservation strategies and ecological management in the face of continuously changing biodiversity patterns., Competing Interests: Declaration of competing interest The authors have no financial/personal interest or belief that could affect their objectivity to declare., (Copyright © 2023 Elsevier B.V. All rights reserved.)